diff --git a/src/share/vm/gc/parallel/gcTaskThread.cpp b/src/share/vm/gc/parallel/gcTaskThread.cpp
index 48eb3c4..8570f71 100644
--- a/src/share/vm/gc/parallel/gcTaskThread.cpp
+++ b/src/share/vm/gc/parallel/gcTaskThread.cpp
@@ -54,8 +54,24 @@ GCTaskThread::~GCTaskThread() {
   }
 }
 
+void GCTaskThread::add_task_timestamp(char* name, jlong t_entry, jlong t_exit) {
+
+  if (_time_stamp_index < GCTaskTimeStampEntries) {
+    GCTaskTimeStamp* time_stamp = time_stamp_at(_time_stamp_index);
+    time_stamp->set_name(name);
+    time_stamp->set_entry_time(t_entry);
+    time_stamp->set_exit_time(t_exit);
+
+    // Update the index after we have set up the entry correctly since
+    // GCTaskThread::print_task_time_stamps() may read this value concurrently.
+    _time_stamp_index++;
+  }
+  // Else silently discard the log entry
+  assert(_time_stamp_index <= GCTaskTimeStampEntries, "Invariant");
+}
+
 GCTaskTimeStamp* GCTaskThread::time_stamp_at(uint index) {
-  guarantee(index < GCTaskTimeStampEntries, "increase GCTaskTimeStampEntries");
+  assert(index < GCTaskTimeStampEntries, "Precondition");
   if (_time_stamps == NULL) {
     // We allocate the _time_stamps array lazily since logging can be enabled dynamically
     GCTaskTimeStamp* time_stamps = NEW_C_HEAP_ARRAY(GCTaskTimeStamp, GCTaskTimeStampEntries, mtGC);
@@ -65,7 +81,6 @@ GCTaskTimeStamp* GCTaskThread::time_stamp_at(uint index) {
       FREE_C_HEAP_ARRAY(GCTaskTimeStamp, time_stamps);
     }
   }
-
   return &(_time_stamps[index]);
 }
 
@@ -75,8 +90,10 @@ void GCTaskThread::print_task_time_stamps() {
   // Since _time_stamps is now lazily allocated we need to check that it
   // has in fact been allocated when calling this function.
   if (_time_stamps != NULL) {
-    log_debug(gc, task, time)("GC-Thread %u entries: %d", id(), _time_stamp_index);
-    for(uint i=0; i<_time_stamp_index; i++) {
+    assert(_time_stamp_index <= GCTaskTimeStampEntries, "Sanity");
+    const uint max_index = _time_stamp_index;
+    log_debug(gc, task, time)("GC-Thread %u entries: %d", id(), max_index);
+    for (uint i = 0; i < max_index; i++) {
       GCTaskTimeStamp* time_stamp = time_stamp_at(i);
       log_debug(gc, task, time)("\t[ %s " JLONG_FORMAT " " JLONG_FORMAT " ]",
                                 time_stamp->name(),
@@ -144,16 +161,7 @@ void GCTaskThread::run() {
 
         if (log_is_enabled(Debug, gc, task, time)) {
           timer.update();
-
-          GCTaskTimeStamp* time_stamp = time_stamp_at(_time_stamp_index);
-
-          time_stamp->set_name(name);
-          time_stamp->set_entry_time(entry_time);
-          time_stamp->set_exit_time(timer.ticks());
-
-          // Update the index after we have set up the entry correctly since
-          // GCTaskThread::print_task_time_stamps() may read this value concurrently.
-          _time_stamp_index++;
+          add_task_timestamp(name, entry_time, timer.ticks());
         }
       } else {
         // idle tasks complete outside the normal accounting
diff --git a/src/share/vm/gc/parallel/gcTaskThread.hpp b/src/share/vm/gc/parallel/gcTaskThread.hpp
index 59e6286..db58cd0 100644
--- a/src/share/vm/gc/parallel/gcTaskThread.hpp
+++ b/src/share/vm/gc/parallel/gcTaskThread.hpp
@@ -45,6 +45,7 @@ private:
   uint _time_stamp_index;
 
   GCTaskTimeStamp* time_stamp_at(uint index);
+  void add_task_timestamp(char* name, jlong t_entry, jlong t_exit);
 
   bool _is_working;                     // True if participating in GC tasks